Pistons for internal combustion engines



July .15, 1958 J. BURNAND PISTONS FOR INTERNAL COMBUSTION ENGINES '7 Sheets-Sheet 1 Filed May 24. 1955 I'M EM A? Jab 1V iamwyfio HM L M HrroR/vg r y 19 8 J. BURNAND 2,843,433

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PISTONS FOR INTERNAL COMBUSTION ENGINES Filed May 24, 1955 7 Sheets-Sheet 4 i 5 g k g 66 53 r A\ firromvirs July 15, 1958 J. BURNAND 2,343,433

- PISTONS FOR INTERNAL COMBUSTION ENGINES Filed May 24, 1955 7 Sheets-Sheet 5 FIGS /9 rro R NEVS July 15, 1958 J. BURNAND 2,843,433

PISTONS FOR INTERNAL COMBUSTION ENGINES Filed May 24, 1955 7 Sheets-Sheet 6 u s7 B --58 i L r l I July 15, 1958 J. BURNAND 2,843,433

PISTONS FOR INTERNAL COMBUSTION ENGINES Filed May 24, 1955 7 Sheets-Sheet 7 EL: I03

{III/1111110,?! will I I [A/ new roR .TaH/v BURN/Mm 2,843,433 Patented July 15, 1958 PISTONS FOR INTERNAL COMBUSTION ENGINES John Burnand, Teddington, England Application May 24, 1955, Serial No. 510,7d7

Claims priority, application Great Britain October 21, 1954 13 Claims. (Cl. 309-14) This invention is concerned with improvements in or relating to internal combustion engines and more particularly to diesel engines.

According to the present invention there is provided a piston comprising a head, a strut, upper bearing means received by the strut and lower bearing means urged toward the upper bearing means by a member threaded upon the head or a part secured thereto or formed integrally therewith.

The strut may be formed intergrally with or be secured to the head and when so formed it preferably extends below the lower bearing means a thread being provided upon the extended part so that the member which urges the lower bearing means toward the upper bearing means may be threaded thereon.

On the other hand the strut may be an independent piece received by the head in which case the head preferably extends below the lower bearing means and is threaded to receive the member for urging the upper and lower bearing means together.

The upper bearing means preferably comprise a single saddle bearing for engaging the entire upper surface of a gudgeon pin formed integrally with a piston rod so that the load exerted upon the head may be spread across the whole of the gudgeon pin thereby avoiding the application of a bending moment to the pin, and the strut is preferably so formed as to provide a backing for substantially the whole ofthe length of the upper bearing means.

Where the strut is integral with the head it preferably.

comprises a central solidboss extending from the underface of the head and merging downwardly into an annular wall in which are diametrically opposed apertures for receiving the upper and lower bearing means and gudgeon pin, a rib extending across between the tops of the apertures upper bearing means.

According to a further feature of the present invention there is provided a piston comprising a heads strut, upper bearing means received by the strut and lower bearing means urged toward said upper bearing means by a member threaded on to the strut, the strut carrying a thrust pad directed toward that side of the piston liable to greatest load and adapted in operation of the piston to ride up on an oil film formed upon the cylinder wall whereby the wear upon that side of the piston may be reduced and lubrication to that side of the piston may be eifected.

In order that the present invention may be well understood there will now be described some embodiments thereof, given by way of example only, reference being had to the accompanying drawings in which,

Figures 1 and 2 are longitudinal cross sections piston in planes normal to one another;

Figure 3 is a plan view of the lower bearings,

Figures 4 and 5 are longitudinal cross sections of a further embodiment of the piston, in planes normal to one another,

Figure 6 is a View on the underside of Figure 5,

of the and forming a continuous backing for the.

Figure 7 is an elevation of the bearings of Figure 5,

Figure 8 is a part sectional elevation of part of the gudgeon pin and piston rod,

Figure 9 is an elevation of a part of a piston ring,

Figure 10 is a section on the line X--X of Figure 9,

Figure 11 is a plan view of that part of the ring shown in Figure 9, and

Figure 12 is an elevation, partly in section of a further embodiment of piston head for use in the piston shown in Figures 4 to 7.

Referring to Figures 1 to 3 the piston is shown not coupled to a gudgeon pin and piston rod but it is of a form for coupling to a gudgeon pin and piston rod such as is shown in Figure 11, wherein the gudgeon pin ii is integral withthe piston rod 2 so as to present a semicircular upper bearing surface along the length of the gudgeon pin, oil galleries 2a and a central oil hole 2b being provided for lubricating the bearing surfaces.

The piston in Figures 1 to 3 comprises a head 3 from which depends a skirt 4 of a thickness substantially equal to that of the head to allow even heat distribution and even shrinking to avoid piping and cracks. Received within the head 3 is a strut 4a of an external diameter slightly less than the internal diameter of the head. The strut 4a comprises a circular head piece 5 from which depends a skirt 6 which surrounds two intersecting ribs "7, 8. The ribs 7 and 8 and the skirt 6 are recessed to receive upper bearing piece 9 in the form of a saddle which will ride upon the upper surface of the gudgeon pin. To hold the gudgeon pin and piston together a pair of lower half bearings ltd, are provided in which the gudgeon pin lower faces ride, the bearings it), each upstanding from plates 12, which rest upon a ring 14 which threads into the skirt, bearing against the underface of the plates outside a flange 15, depending from each plate 12. The plates and bearings provide an aperture 17 in in which the piston rod may oscillate.

The upper bearing piece 9 is located against rotation by a key 18 engaging that piece and the strut and the ring 14 is locked by a pin 19. r If desired the lower bearings may be formed separately from the plates and located thereupon by pins. The thread upon the skirt and the ring is preferably a buttress thread.

About the head are located L-section rings 20, 21 oppositely directed and held against a shoulder 22 by a clamping ring 23 which is locked by pins 2d. Ring serves as a compression ring and ring 21 as a scraper.

About the foot of the skirt is a further L-section ring 25 clamped against the skirt and by an oppositely directed L-section ring 26 having a root threaded into the skirt, and being locked thereto by a pin 27. Ring 25 acts as a loW compression ring to prevent gases reaching the sump and ring 26 as a scraper.

In Figures 4 to 7 there is shown a piston coupled to a piston rod 5b integral with which is a gudgeon pin ill. The piston in this embodiment comprises a head 52 having an annular depending skirt 53 extending buttress threaded into a strut 54 having a recess 55 in which is received an upper bearing piece 5'16 extending over the gudgeon pin 51. The gudgeon pin is held in the upper hearing by two half bearings 57, 5% held in the strut by an externally threaded ring 5'9, itself locked to the body by a split pin 60.

The end face 61 of the head slopes so that as viewed in Figure 4 the piston is urged when under load towards the left, and toward that side which tends to wear the most rapidly.

The head is locked to the strut by a tapering split pin 62 and has a depending annular outer skirt 6E5 internally threaded to receive a ring 64 which clamps against the end of the outerskirt an L ring65, the ring 64 being locked in position by a tapered split pin 65a. The ring 65 acts as a compression ring and the ring 64 as a scraper.

The upper bearing 56 is keyed tothe piston body by a locating pin 66 and extends beyond the outer periphery of the strut as at 67 (Figure 5) where splash holes 68 and galleries 69 are provided for admitting oil to a lubricating groove 70 on the gudgeon pin.

Each half bearing 57, 58 includes a semi-circular platform 71 having a depending flange '72. Each half bearing along its straight side has a recess 73 which receives the piston rod and permits the angular movement thereof The stint is generally circular at its upper part but lower portion, see Figure 2 particularly, is only part circular, a part being removed for the mounting of a thrust pad 5. This pad is pivoted on an externally threaded member '76 which is secured by nuts '77, 73 on a spring plate "I? which clamps on to a rectangular boss 3t on the strut.

The piston body may be arranged so that the axis of the gudgeon pin is offset as viewed in Figure 4 to the right of the axis of the piston, to further urge the piston to the left to take up wear and hence reduce slap.

In operation the piston for example on a power stroke or compression stroke receives a load on the sloping end face which with the gudgeon pin axis offset from the piston axis causes the piston to be urged to the left as viewed in Figure 4 thereby preventing slap of the piston. This thrust causes the thrust pad to bear towards the cylinder wall but the mounting of the thrust pad and the shape of its upper and lower edges permits the pad during each stroke to ride up on to and along the top of the oil film formed on the cylinder wall so that a properly lubricated bearing is provided between the piston and cylinder wall at the part placed under greatest pressure by the anti-slap construction of the piston.

The lubrication of the split bearing is effected by a groove 81 formed in each half bearing which groove is supplied with splash oil at the end faces of the gudgeon pm.

It will be appreciated that instead of the gudgeon pin and connecting rod shown may be used the gudgeon pin and connecting rod illustrated in Figure 8 and referred to above.

In Figure 15 is shown an alternative form of piston head for use with the piston shown in Figures 4 to 7 and I at present prefer this alternative construction in which the head 152 has a depending inner annular skirt 153 buttress threaded to engage a strut such as is shown in Figures 4 to 7. The head 152 has also a depending outer annular skirt 154 which has a plurality of circumferential channels 155 in each of which is a groove 156. In each channel 155 and its groove 156 is accommodated a piston ring 157 which is a split ring having in cross section a substantially semi-circular centre part 158 received in the groove 156 and on either side of the part 158 a flange 159. The ring at its ends is provided with male and female portions 160 and 16]. whereby the ring forms a continuous seal about the piston.

Where the piston according to the present invention is for use in small engines, for example having a bore of the order of 88 mm. it may be preferred that the piston rings should be continuous, that is to say they should not be split rings. Where however the piston is for usein larger engines such as marine engines and stationary engines for generating plant, it is preferred to use split n'ngs but to seal the split in at least the topmost ring, that is the compression ring.

In Figures 9 to 11 is shown a preferred form of ring with a sealing arrangement. 100 and to seal the space between 101 extending across the ends. the back plate are spot welded ribs 102 which are received in recesses 103 in the ring and a top rib 104. The recesses are of sufiicient length to permit relative movement of the plate and ring upon expansion and contraction of the ring. The plate extends beneath the surface split The ring is designated its ends is a back plate Upon the outer face of Cal against which the ring is held and a slot is provided in that surface to receive the ring. Where the top ring is a split ring and is sealed and the other rings are split rings unsealed, I prefer that the unsealed rings should be adjusted so that the splits are directed toward that side of the piston subject to greatest wear.

Various modifications may be made to the above described embodiments. For example where the piston is for use in a light and inexpensive engine, the connecting rod may be tubular and at the small end split longitudinally, the U-shaped halves being turned outwardly to extend in opposite directions normal to the axis of the piston rod. These arms receive a pin, the upper bearing resting on the pin and the arms bearing against the lower bearing pieces. Furthermore in the case of the embodiment shown in Figures 1 to 3 the strut may be of reduced dimeter below at its central part and may have at its base two diametrically opposed outwardly projecting flanges, the flanges being recessed to form bearings for a gudgeon pin which is then held in by lower bearings bolted direct to the flanges of the strut which would then be secured to the head. In such case the ring 14 is dispensed with. If desired one or both of the intersecting walls in the main strut -may be dispensed with.

In all of the embodiments described it will be seen that the piston head is supported at or about its centre and that the load is distributed over the length of the gudgeon pin. By this construction the piston is rendered robust yet simple.

Furthermore it will be seen that in each of the embodiments described there presence of masses of metal integral with parts of lesser dimension is avoided. In known forms of piston gudgeon pin bosses are formed integrally with the thin piston skirt. Such bosses do not expand nor contract uniformly with the skirt and hence internal stresses are set up which limit the life of the piston. In the piston according to the present invention such internal stresses are avoided by the generally uniform distribution of the metal and by the piston being of circular form at those parts liable to greatest temperature change. In ad dition the piston according to the present invention is not a single unit but incorporates a number of parts which permits slight relative movement between the parts should neighbouring parts expand and contract in dissimilar fashion.

A further feature of importance is that the piston head at least of Figures 1, 2, 4, 5, 6, 7, and 12 can be produced by forging so as to provide a head of great strength.

What is claimed is:

l. A piston comprising a head, a strut located beneath said head to support at least the central part of said head and removable from the piston, upper bearing means located beneath and abutting said strut, removable lower bearing pieces and a lower bearing retaining member making screw threaded engagement with a part coupled to said head.

2. A piston comprising a head, a strut located beneath a central part of said head and detachably secured thereto,

upper bearing means located beneath and abutting said strut removable lower bearing pieces and a lower bearing retaining member making screw threaded engagement with 21 depending portion of said strut.

3. A piston comprising a head, a skirt integral with d and depending from said head, a strut removably supported within said skirt in abutment with the underside of said head, upper bearing means abutting the underside of said strut, removable lower bearing pieces and a lower bearing retaining member making screw threaded engagement with said skirt and retaining said strut therewithin.

4. A piston comprising a head, a skirt depending from said head, a strut received by said skirt and abutting the underface of said head, an upper saddle bearing received in a recess in the underface of said strut, a circular two part lower bearing plate,received by said skirt and defining an aperture for the passage of connecting rod, a lower bearing member carried by each of said parts of said lower bearing plate and an externally threaded ring engaging a screw threaded part of said skirt and abutting the underface of said two part bearing plate.

5. A piston comprising a circular head, a screw threaded boss extending from the underface of said head, a strut having a screw threaded part engaging the screw threaded boss, an upper saddle bearing received by said strut, a circular two part lower bearing plate eccentric with respect to said head, received by said strut and defining an aperture for the passage of a connecting. rod, a lower bearing member carried by each part of said bearing plate and an externally threaded ring engaging a threaded part of said skirt and engaging the underside of said two part bearing plate.

6. A piston according to claim 5, in which said head is inclined having its highest part in the plane including the centres of said head and said bearing plate and at that side of the piston axis remote from said bearing plate centre and in which a thrust pad is pivotally carried by a resilient plate on said skirt, said pad being in said plane and beneath said highest part.

7. A piston comprising a head, a strut located beneath said head to support at least the central part of said head and removable from the piston, upper bearing means located beneath and abutting said strut, removable lower bearing pieces, a lower bearing retaining member making screw threaded engagement with a part coupled to said head, and a pair of piston rings located adjacent said head and each having in section a part normal to the piston axis and a part parallel with said axis, said rings abutting with those parts normal to said axis adjacent one another.

8. A piston comprising a head, a strut located beneath said head to support at least the central part of said head and removable from the piston, upper bearing means located beneath and abutting said strut, removable lower bearing pieces, a lower bearing retaining member making screw threaded engagement with a part coupled to said head, at least one split piston ring having a part normal to the axis of the piston, and a part parallel to said axis, the ends of said ring each defining a slot in said parts normal to and parallel with said axis, and a sealing plate having a part parallel to said axis and a part normal to said axis, nested in said piston ring and bridging said ends of said piston ring and ribs on said sealing plate extending into said slots.

\ MlMulllhillulltullllllliiil iii 9. A piston comprising a head, a strut located beneath said head to support at least the central part of said head, and removable from the piston, upper bearing means located beneath and abutting said strut, removable lower bearing pieces, a lower bearing retaining member making screw threaded engagement with a part coupled to said head, and at least one piston ring having in section planar marginal parts and a concave centre part, said piston defining an external groove with a central curved depression, said ring being received by said groove and said depression.

10. A piston according to claim 9 in which said ring is split, the ends of said ring defining slots and projections, said slots of one of said ends receiving the pro jections of said other end.

11. A piston comprising a head, a strut located beneath said head to support at least thecentral part of said head and being removable from the piston, upper bearing means associated with the underside of said strut, and removable lower bearing pieces and a lower bearing retaining member making screw threaded engagement with a part coupled to said head.

12. A piston comprising a head, a strut located beneath a central part of said head and detachably secured thereto, upper bearing means associated with the underside of said strut, and removable lower bearing pieces and a lower bearing retaining member making screw threaded engagement with a depending portion of said strut.

13. A piston comprising a head, a skirt integral with and depending from said head, a strut removably supported within said skirt, and abutting the under side of said head, upper bearing means associated with the underside of said strut, and removable lower bearing pieces and a lower bearing retaining member making screw threaded engagement with said skirt to retain said strut in assembled relationship with said skirt.

References Cited in the file of this patent UNITED STATES PATENTS 1,076,326 Strite Oct. 21, 1913 1,394,898 Harriman Oct. 25, 1921 1,569,966 Claypool Ian. 19, 1926 1,603,135 Mayes Oct. 12, 1926 2,198,623 Kastler Apr. 30, 1940 2,563,371 Rippingille Aug. 7, 1951 

